LONDON, March 12 (Reuters) - Britain could face at least 12
gigawatts (GW) of power plant capacity going off line by the end
of 2023 due to tighter European Union pollution regulation,
Reuters calculations based on government data showed on
Wednesday.

Britain is at risk of a severe power capacity crunch in the
2020s as ageing nuclear power stations come to the end of their
life and coal and gas plants shut down because they cannot
afford to add costly technology to reduce greenhouse gas
emissions to comply with EU law.

Britain's Department for Environment, Food and Rural Affairs
(Defra) has published a list of power plants whose operators
have requested they are exempted from the EU's Industrials
Emissions Directive - meaning they are not slated for expensive
upgrades and will therefore close over the next nine years.

The list, which included plants run by SSE Plc, EDF
and RWE, did not show any details of capacity
which could be closed, but this number is important for the
industry in order to calculate how much replacement capacity
might be required.

Operators can still change their minds on the opt-out up
until Jan. 1, 2016.

Under the EU directive, power plants in the bloc have to
control and reduce the impact of their emissions on the
environment. In most cases this involves retrofitting their
plants with expensive technology.

Power plant operators have had to inform their relevant
environment regulator about which stations have chosen not to
install such technology.

Plants can run without upgrades for 17,500 hours starting
Jan. 1, 2016, or to the end of 2023, whichever comes first.

Across Europe, power generators are shutting down or
mothballing plants as they try to cut costs, after being taken
by surprise by a surge in output from renewable energy sources,
making many gas and coal plants redundant and leading to a
collapse in wholesale power prices.

In Britain the situation is particularly acute.

"This (12 GW total) could tighten up capacity margins quite
a bit by the end of the decade (from 2019) as the first plants
go offline," said Trevor Sikorski, analyst at consultancy Energy
Aspects.

Without any immediate replacements, Britain's energy
watchdog Ofgen has warned blackouts might be possible and that
avoiding supply shortages will carry a price.

A spokeswoman from the UK's Department of Energy and Climate
Change said Britain is trying to build a "diverse, low-carbon
and efficient energy mix to reduce our emissions and give
consumers the best deal"